Hello my friend, yes it is very fun, I have a power transistor deficiency for 4b stt. I recovered my Goldmund clone, I'm missing a mosfet.
Ah, MPS92. You can get it from both Reichelt and Farnel, but Reichelt sells CDIL and Farnell sells their own brand "Multicomp pro". I suspect that they are from similar source. I have tested CDIL transistors with curve tracer and I have found that they are good. Also, in a circuit I have measured decent noise flor. There is nothing to loose, they cost pennies, just transportation cost may be high.
Have a pleasant week end.
ONSEMI mpsa92/42 is original in the country I am in, there is an oscillation problem, I want to use a different transistor in these goldmunds
I'm wondering if anyone here can help me. I recently came into possession of a whole load of Bryston amps, they're branded Sonics and came out of an IMAX cinema. There are a lot of amps, configured as 800x and 600x. The 800 was set up as a mono stereo amp, kind of like a 7b, the 600x is set up as stereo, but one of the channels is actually 2 modules bridged, so 2 channel but one channel is double the power of the other. They had custom input boards, with eq, delay, crossover etc, but sadly the amps had the input boards removed before I got them. I'm trying to restore them to usable condition with input stages. I wish to set up one 800x for bridge mono sub duties. I've found 2 solutions, I either buy the small DOA33 board, or the fully complete Rev 3 Bryston Clone input board on Aliexpress. The problem I have is that the fully completed board comes out to around £70. The DOA33 however is only £30. My question is, can the DOA33 board be set up for a balanced input. To configure it as bridged mono, I need to send the output of one side of the op amp into the inverting input of the other. But the board does not allow that. From looking at the schematic it seems that the inverting input is tied to ground. I am wondering if I disconnected the 1k to ground, I can then use both the inverting and non inverting inputs. For balanced and for bridged purposes. If this doesnt work then I'll have to get the fully completed board with the bridge and balance switches already installed, but I have a lot of these amps so that will start to get expensive.
Some pics of the amp
Some pics of the amp
I haven't got any boards yet, I can't decide between these 2. If I can bridge the DOA33 then I'll go for that, but I'm not sure its possible.
The modules say 7B on the PCB, there are extra sets of output transistors connected to the board so they will be more powerful than the 3b. The Transformers are also huge, they were driving 2 x 12 inch bass drivers per channel when installed in the IMAX
https://www.aliexpress.com/item/1005003657685410.html
https://www.aliexpress.com/item/1005003700885396.html
The modules say 7B on the PCB, there are extra sets of output transistors connected to the board so they will be more powerful than the 3b. The Transformers are also huge, they were driving 2 x 12 inch bass drivers per channel when installed in the IMAX
https://www.aliexpress.com/item/1005003657685410.html
https://www.aliexpress.com/item/1005003700885396.html
I realized later that there are extra output transistors connected to the board,
28b Build
I have just built the 28b clone which works well, but I do have a question regarding the biasing.
I have had the amp on the bench with no input or output connected, whilst checking the bias and dc offset. The dc offset seems stable and fluctuates around + or - 2mV so all seems good there. The bias creeps up over a long period of time, it stayed at around 23mV across R45 for a couple of hours. I then left the amp alone for a further few hours and when I returned it was sitting around 45mV and was obviously quite warm.
The question I have is do I tweak this down after leaving it on for a number of hours or is it likely to go through a cycle of up and down and I just missed it going back down?
Any help would be much appreciated!
I have just built the 28b clone which works well, but I do have a question regarding the biasing.
I have had the amp on the bench with no input or output connected, whilst checking the bias and dc offset. The dc offset seems stable and fluctuates around + or - 2mV so all seems good there. The bias creeps up over a long period of time, it stayed at around 23mV across R45 for a couple of hours. I then left the amp alone for a further few hours and when I returned it was sitting around 45mV and was obviously quite warm.
The question I have is do I tweak this down after leaving it on for a number of hours or is it likely to go through a cycle of up and down and I just missed it going back down?
Any help would be much appreciated!
Thanks chalky for sharing the solution to the symmetrical IPS with mirror. I found the Stochino design that you mentioned, that uses it: https://worldradiohistory.com/UK/Wireless-World/90s/Electronics-World-1997-04.pdf